Respiratory troubles during sleep, such as Sleep Apnea Syndrome (SAS), are characterized in general by disfunction of the respiratory function during sleep.
There is observed in victims subject to such a syndrome, serious interruption of the sleep with short phases of sleep and resumption of normal respiration, accompanied most often by a short waking of several seconds.
The normal course of sleep, from the condition of light sleep to the condition of deep sleep, passing through a condition of paradoxical sleep, is greatly disturbed, which has consequences in the waking hours of these subjects. They thus have the tendency to be sleepy, and to fall asleep while active, and there is also observed in them a decrease of the intellectual and sexual functions, and the risk of hypertension and cardiac insufficiency.
Respiratory troubles can be of the obstructive or central types.
In the first case, there is observed a total obstruction (obstructive apnea) or partial obstruction (obstructive hypopnea) of the upper respiratory tract whilst the muscular strength is maintained. This type of trouble is often associated with loud snoring.
In the second case, muscular control is absent (central apnea) or decreased (central hypopnea), the upper respiratory tract being open.
Obstructive troubles represent the large majority of nocturnal respiratory troubles.
Ordinarily, the diagnosis of respiratory troubles during sleep is carried out in a sleep laboratory, thanks to the recordation and study of numerous interconnected parameters:
during sleep: electroencephalogram, electrooculogram, electro-myogram, PA1 as to cardio-respiratory function: electrocardiogram, respiratory frequency, nasal and/or buccal flow, thoracic and abdominal movements, arterial saturation with oxygen, snoring. PA1 not having the drawbacks of known apparatus; PA1 usable both in a sleep laboratory, which is to say in a hospital environment, and at the patient's home; PA1 adapted to permit determining a reliable image of all nasal and/or buccal respiratory flow of a patient, which image is adapted to help in the diagnosis and/or treatment of sleep respiratory troubles, and this in an easy and effective manner; PA1 permitting determining the respiratory flow image of the patient from variations of the current consumed by the motor of the blower supplying the patient with respiratory gas comprising oxygen, such as air; PA1 and which will be of reasonable cost and easy to produce. PA1 the current consumed by the blower motor is continuously measured and a consumed current signal is thus derived, PA1 the consumed current signal is processed, PA1 an image of the nasal and/or buccal respiratory flow of the user is determined from the processed current signal. PA1 processing of the consumed current signal is carried out by filtering, integration and/or amplification of said signal, PA1 there can be a step of memorizing and/or displaying the image of the nasal and/or buccal respiratory flow, PA1 the obtained image is the image of nasal or bucco-nasal respiratory flow, PA1 there is moreover determined an image of a buccal respiratory flow by means of at least one thermistance, PA1 determining the mean value (V.sub.1) of the respiratory flow image during a time t.sub.1 and the mean value (V.sub.2) of the respiratory flow image during a time t.sub.2, with t.sub.1 &gt;t.sub.2, PA1 calculating the value .DELTA.(V) wherein .DELTA.(V)=V.sub.1 -V.sub.2, PA1 deriving the valve .DELTA.(V) of information concerning the inhalation or exhalation phase, PA1 determining the maximum values (I.sub.max) and minimum values (I.sub.min) of the flow rate image during a time t corresponding to at least one portion of the duration of a respiratory cycle, PA1 determining the amplitude (A) of the image of the flow wherein A=I.sub.max -I.sub.min, PA1 comparing the amplitude (A) of the flow rate image with at least one threshold amplitude value (As), PA1 also the step of determining from the comparison of amplitude (A) with at least one threshold amplitude value (As), information as to the presence or absence of respiratory trouble, PA1 further performing the step of modifying the pressure of the gas delivered by the blower as a function of the result of the comparison of the amplitude (A) with at least one threshold amplitude value (As), PA1 setting t.sub.1 equal to at least about 5 seconds and preferably to at about 15 seconds and/or t.sub.2 is equal to at most about 1 second and preferably at most about 0.125 second. PA1 means to administer a respiratory gas at at least one level of pressure, comprising at least one blower driven by a motor, PA1 supply means comprising at least one conduit for supplying said respiratory gas, connecting the blower to the nasal and/or buccal respiratory passage of the user, PA1 means for measuring the current consumed by the blower motor so as to derive a consumed current signal, PA1 means for processing said consumed current signal, PA1 means for memorizing an image of the nasal and/or buccal respiratory flow of the user. PA1 the treatment means comprise a filter, an integrator and/or a signal amplifier, PA1 it moreover comprises means for processing the image of the respiratory nasal and/or buccal flow of the user, permitting to derive therefrom information as to the presence or absence of respiratory trouble, PA1 it is of the type with one or two pressure levels.
The diagnoses of these sleep pathologies is recent and its use is difficult and requires hospitalization of the subject for one or two nights.
The treatment of sleep respiratory troubles ordinarily uses an apparatus permitting maintaining the upper respiratory tract open.
This apparatus comprises most often a positive pressure apparatus with a mask (CPAP), in which an ambient air compression means, controlled by a control device, delivers into a conduit and then into a mask placed over the nose of the patient in a sealed manner, air under pressure.
The control device compares the value of the pressure in the mask to a reference value of adjusted pressure and, according to the measured difference, adjusts a control signal which it delivers to the ambient air compression means.
At present, the reference value of pressure to be applied in the mask of the patient is determined empirically in the sleep laboratory by progressive increase from an initial reference value, an observation of the consequences on the respiratory troubles, the selected value being the first value for which there is observed uninterrupted normal sleep.
There exist diagnostic and/or treatment devices for these nocturnal respiratory troubles, detecting apnea or hypopnea, but not differentiating between the central and obstructive events.
Other permits, starting from an analysis of the frequency of the pressure signal measured in the mask, detecting snoring and the treatment apparatus thus adjusts the reference value of pressure to suppress snoring.
Still others, after having detected apnea, send to the mask on the patient a pressure impulse and study the possible echo: if there is no echo, the event is central, and if there is an echo, the event is obstructive.
Such apparatus are particularly described in French patents FR-A-2663547 and FR-A-2674133.
However, so as to be able to establish a correct diagnosis of the respiratory troubles (apneas, hypopneas, pathology of increased resistance . . . ) and/or to determine and/or to initiate a suitable and effective treatment, it may be necessary, or even indispensable, that the practitioner, which is to say the doctor or the like, have a reliable image representative of the sequence of the different inhalation and exhalation phases of his patient, which is to say the image of the respiratory flow rate or flow of the subject.
However, the existing processes and apparatus either do not permit such a reliable and effective determination of the image of said respiratory flow rate, or require the use of flow rate detectors, which flow rate detectors cannot be considered as a satisfactory solution, to the extent to which these latter give rise on the one hand to a complication of the overall structure of the apparatus, and hence its size, and, on the other hand, a substantial increase of the cost of the latter.
Moreover, the results obtained with flow rate detectors are not very precise because the latter do not permit taking into account the problem of persons breathing with the mouth open and obtaining a correct image of this nasal respiratory flow.
Thus, a large number of persons suffering from respiratory troubles, in particularly of the obstructive type, have the habit of breathing simultaneously from the nose and from the mouth. However, such buccal respiration appears at present on the nasal respiratory flow image as an apnea, given that it gives rise to an absence of buccal respiratory flow.
Accordingly, it will be easily seen that in similar circumstances, the diagnoses and/or the subsequent treatment can only be incorrect or incomplete.